* sysdeps/unix/sysv/linux/getdents.c (__GETDENTS): Use union type for

	pointers that can alias.
	Reported by Daniel Jacobowitz <drow@mvista.com>.

diff --git a/ChangeLog b/ChangeLog
index 26dcd78a3c34a4528301904265b73c2a5e662475..cf31c4f3ab4c27224307aa7f411eea9887ab8a68 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2002-11-02  Roland McGrath  <roland@redhat.com>
 
+       * sysdeps/unix/sysv/linux/getdents.c (__GETDENTS): Use union type for
+       pointers that can alias.
+       Reported by Daniel Jacobowitz <drow@mvista.com>.
+
        * sysdeps/unix/bsd/bsd4.4/freebsd/bits/typesizes.h: New file.
 
 2002-11-02  Roland McGrath  <roland@redhat.com>

diff --git a/sysdeps/unix/sysv/linux/getdents.c b/sysdeps/unix/sysv/linux/getdents.c
index 6dc9d714b5b2c93c9b519e3dcfe42ac9f40e0241..e5796c329cb5bd2e880e947364ef4392f3662f6a 100644 (file)
--- a/sysdeps/unix/sysv/linux/getdents.c
+++ b/sysdeps/unix/sysv/linux/getdents.c
@@ -97,7 +97,6 @@ ssize_t
 internal_function
 __GETDENTS (int fd, char *buf, size_t nbytes)
 {
-  DIRENT_TYPE *dp;
   off64_t last_offset = -1;
   ssize_t retval;
 
@@ -109,7 +108,12 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
 # ifndef __ASSUME_GETDENTS64_SYSCALL
       int saved_errno = errno;
 # endif
-      char *kbuf = buf;
+      union
+      {
+       struct kernel_dirent64 k;
+       DIRENT_TYPE u;
+       char b[1];
+      } *kbuf = (void *) buf, *outp, *inp;
       size_t kbytes = nbytes;
       if (offsetof (DIRENT_TYPE, d_name)
          < offsetof (struct kernel_dirent64, d_name)
@@ -125,7 +129,6 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
       if (retval != -1 && errno != -EINVAL)
 # endif
        {
-         struct kernel_dirent64 *kdp;
          const size_t size_diff = (offsetof (struct kernel_dirent64, d_name)
                                    - offsetof (DIRENT_TYPE, d_name));
 
@@ -137,31 +140,43 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
             need, don't do any conversions.  */
          if (offsetof (DIRENT_TYPE, d_name)
              == offsetof (struct kernel_dirent64, d_name)
-             && sizeof (dp->d_ino) == sizeof (kdp->d_ino)
-             && sizeof (dp->d_off) == sizeof (kdp->d_off))
+             && sizeof (outp->u.d_ino) == sizeof (inp->k.d_ino)
+             && sizeof (outp->u.d_off) == sizeof (inp->k.d_off))
            return retval;
 
-         dp = (DIRENT_TYPE *)buf;
-         kdp = (struct kernel_dirent64 *) kbuf;
-         while ((char *) kdp < kbuf + retval)
+         /* These two pointers might alias the same memory buffer.
+            Standard C requires that we always use the same type for them,
+            so we must use the union type.  */
+         inp = kbuf;
+         outp = (void *) buf;
+
+         while (&inp->b < &kbuf->b + retval)
            {
              const size_t alignment = __alignof__ (DIRENT_TYPE);
-             /* Since kdp->d_reclen is already aligned for the kernel
+             /* Since inp->k.d_reclen is already aligned for the kernel
                 structure this may compute a value that is bigger
                 than necessary.  */
-             size_t old_reclen = kdp->d_reclen;
+             size_t old_reclen = inp->k.d_reclen;
              size_t new_reclen = ((old_reclen - size_diff + alignment - 1)
                                  & ~(alignment - 1));
-             uint64_t d_ino = kdp->d_ino;
-             int64_t d_off = kdp->d_off;
-             unsigned char d_type = kdp->d_type;
-
-             DIRENT_SET_DP_INO (dp, d_ino);
-             dp->d_off = d_off;
-             if ((sizeof (dp->d_ino) != sizeof (kdp->d_ino)
-                  && dp->d_ino != d_ino)
-                 || (sizeof (dp->d_off) != sizeof (kdp->d_off)
-                     && dp->d_off != d_off))
+
+             /* Copy the data out of the old structure into temporary space.
+                Then copy the name, which may overlap if BUF == KBUF.  */
+             const uint64_t d_ino = inp->k.d_ino;
+             const int64_t d_off = inp->k.d_off;
+             const uint8_t d_type = inp->k.d_type;
+
+             memmove (outp->u.d_name, inp->k.d_name,
+                      old_reclen - offsetof (struct kernel_dirent64, d_name));
+
+             /* Now we have copied the data from INP and access only OUTP.  */
+
+             DIRENT_SET_DP_INO (&outp->u, d_ino);
+             outp->u.d_off = d_off;
+             if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)
+                  && outp->u.d_ino != d_ino)
+                 || (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)
+                     && outp->u.d_off != d_off))
                {
                  /* Overflow.  If there was at least one entry
                     before this one, return them without error,
@@ -169,23 +184,21 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
                  if (last_offset != -1)
                    {
                      __lseek64 (fd, last_offset, SEEK_SET);
-                     return (char *) dp - buf;
+                     return outp->b - buf;
                    }
                  __set_errno (EOVERFLOW);
                  return -1;
                }
 
              last_offset = d_off;
-             dp->d_reclen = new_reclen;
-             dp->d_type = d_type;
-             memmove (dp->d_name, kdp->d_name,
-                      old_reclen - offsetof (struct kernel_dirent64, d_name));
+             outp->u.d_reclen = new_reclen;
+             outp->u.d_type = d_type;
 
-             dp = (DIRENT_TYPE *) ((char *) dp + new_reclen);
-             kdp = (struct kernel_dirent64 *) ((char *) kdp + old_reclen);
+             inp = (void *) inp + old_reclen;
+             outp = (void *) outp + new_reclen;
            }
 
-         return (char *) dp - buf;
+         return outp->b - buf;
        }
 
 # ifndef __ASSUME_GETDENTS64_SYSCALL
@@ -205,7 +218,6 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
                         * size_diff),
                      nbytes - size_diff);
 
-    dp = (DIRENT_TYPE *) buf;
     skdp = kdp = __alloca (red_nbytes);
 
     retval = INLINE_SYSCALL (getdents, 3, fd,
@@ -214,6 +226,7 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
     if (retval == -1)
       return -1;
 
+    DIRENT_TYPE *dp = (DIRENT_TYPE *) buf;
     while ((char *) kdp < (char *) skdp + retval)
       {
        const size_t alignment = __alignof__ (DIRENT_TYPE);
@@ -250,7 +263,7 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
        dp = (DIRENT_TYPE *) ((char *) dp + new_reclen);
        kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen);
       }
-    }
 
-  return (char *) dp - buf;
+    return (char *) dp - buf;
+  }
 }